[GreenKeys] TTY Loop Supply

[Don Robert House]

Negative battery is very important when applied to underground cable  
pairs.  If positive battery is applied to the cable pairs it causes  
electrolysis.
The telephone industry dislikes their copper wires to disappear over  
time... and it does not take long for this to happen.
All of our "telegraph" circuits were negative 130 vdc with a positive  
ground.

When you are aboard a ship or aircraft using RADIOTELEGRAPHY you do  
not have this problem and the convention of positive battery and  
negative ground works fine.

Don

DR HOUSE
Associate Manager, Transmission Engineering
Illinois Bell Telephone Co. long retired...
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On 28 Apr 2014, at 5:01 PM, Nick England wrote:

In the same vein, I'm a newcomer to TTY, and am interested in what the  
conventions for wiring were.

All the Navy gear I have been messing with have loop supply POS  
feeding the current limiting resistor, then looping jacks, then set  
jacks, then LINE to NEG (ground). This scheme works fine with various  
converters like the sainted URA-8A which has a tube plate output  
switching to ground. OK so far.
Then I started to hook up a TT-63A regenerative repeater, something  
that ought to be commonly found in USN TTY centers. Input is Neg to Gnd!
Yeah it is easy to drive a grid that way, but how did these things co- 
exist?

Was this a usual thing to mix up loop polarities willy-nilly and stick  
polar relays in between them to get right side up? Or was there a real  
convention that people tried to follow?
Cheers,
Nick
(phone email acct)


On Apr 28, 2014, at 5:14 PM, Chris Elmquist <chrise at pobox.com> wrote:

> I note the "TIP NEGATIVE" notice on the front panel.
> Was that any sort of convention or was the rule that you just had to
> state what the polarity is?
>
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